Certificate of correction



0. C. TRAVER PROTECTIVE ARRANGEMENT Original Filed larch $8. 1926 WW I aJ a a M I1I4I1W I1I I M g N Mn 2 6 4 a. I 7 A0 a 4 l l 7 z Z J V Z a K 1U6 Z #5 0 W 2 Maw z Z Z I I IN I I Feb. 18, 1930.

Invefitor': OHVET C.TTaver, b y His Attorney.

Reissued Feb. 18, 1930 UNITED STATES PATENT OFFICE.

OLIVER G. TRAVER, 0F IRENFIELD, PENNSYIJVANIA, ASSIGNOB TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK PROTECTIVE ARRANGEMENTOriginal No. 1,659,619, dated February 21, 1928, Serial No. 95,757,filed March 18, 1926 Application In: reissue flied February 7, 1929.Serial No. 838,806.

My invention relates to improvements in protective arrangements forelectric systems and more particularly for systems comprismg twoparallel'lines, especially when these are provided with a differentialsystem of protection involvin current transformers which are connecte inseries for normally c rculating current, whereby further protection,such that either line alone may carry as much current as the twotogether, is provided in an economical and satisfactory manner.

My invention will be better understood from the following descriptiontaken in connection with the accompanying drawing, and its scope will bepointed out in the appended claims.

In the accompanying drawing, Fig. 1 illustrates diagrammatically, insingle phase for clearness, an embodiment of my inventron as applied totwo parallel lines provided with a differential system of protection,and Figs. 2 and 3 illustrate diagrammatically, also in single phase,modifications of the embodiment of my invention shown in Fig. 1.

In the several figures of the drawing, two parallel lines, 4 and 5, ofwhich only one phase conductor is shown, are arranged to be connected toa bus through suitable circuit lnterrupters 7 and 8 having trip coils 9and 10. For selectively controlling the opening of the circuitinterrupters 7 and 8 on the occurrence of faults, there may be provideda. difierential protective arrangement which is herein shown ascomprising an over-current relay 11 having a coil 12 and a directionalrelay 13 having cooperating current and 0- tential coils 14 and 15respectively. he directional relay 13 has two sets of contacts, 16 and17 which are connected in series with the trip coils 9 and 10respectively and in series with the contacts 18 of the over-currentrelay 11. The otential coil 15 of the directional relay 13 18 arrangedto be energized from the bus 6 through a potential transformer 19. Inorder that the coil 12 of the over-current rela 11 and the current coil14 of the directions relay 13 may be energized in accordance with thevectorial difi'erence between the currents in corresponding phaseconductors of the lines 4 and 5, they are connected between points 20and 21 of a circuit comprising the secondaries 22 and 23 of currenttransformers energized. respectively from the lines 4 and 5, thesecondaries being connected in series for normally circulating current.These points 20 and 21 are so chosen that with the lines 4 and 5carrying currents in the same direction and the current transformersecondaries 22 and 23 furnishing substantially equal currents, the

pence between the line currents but also in accordance with thevectorial sum of the line currents, in such a manner that either one ofthe lines alone, when the other is out-of service, may carry as muchcurrent as the two lines together without the necessity of readjustingany of the protective apparatus.

In accordance with my invention I accomplish this by aniinductive means24, comprising an inductive winding which is connected in thecirculating current circuit of the current transformer secondaries 22and 23 and which includes at an intermediate point one.of the points 20and 21 in the connection across the normally circulating currentcircuit. Associated with the inductive means and arranged to beenergized therefrom is an electroresponsive device such as anover-current relay" 25 which has an en-' ergizing coil 26 and which isarranged to control the circuits of the trip coils 9. and 10 throughcontacts 27.

In Fig. 1, the inductive means 24 is illustrated as a stationaryinductive means comprising an inductive winding 28 across which therelay coil 26 is connected. With this arrangement, the relay coil 26will be energized by a current which is derived from the line currentsand which is substantially proportional to the vectorial sum thereof,

no matter whether one or both of the lines 4 and 5 is or are in service.Assuming equal currents in the lines 4 and 5, then a currentproportional to that of each of the lines will tend to circulate in thecircuit including the current transformer secondaries 22 and 23 and theinductive winding 28, but no current will flow in the connection betweenthe points 20 and 21, since they have substantially the same potentialunder the conditions assumed. Consequently, the inductive winding 28acts in effect as a reactor and a current substantially equal to onehalfof the sum of the currents in the current transformer secondaries 22 and23, that is, proportional to the sum of the line currents, appears inthe relay coil 26. When this current exceeds that for which the relay 25is set to operate, both of the circuit interrupters 7 and 8 will betripped. If the current in one line, for example, line 4, is greaterthan the current in the line 5, then a current proportional to thecurrent in the line 4 tends to How through one-half of the inductivewinding 28 while a current pro- 30 portional to the current in the line5 tends to flow through the other half in the same direction. Thedifference between these currents appears in the connection between thepoints 20 and 21, since they are not at substantially the samepotential. One-half V of this difference flows in one direction inone-half of the winding 28 and the other half of the difference flows inthe opposite direction in the other half of the winding 28. Consequentlythis winding 28 acts in effect as a reactor and a current substantiallyequal to one-half of the vectorial sum of the currents in the currenttransformer secondaries 22 and 23 appears in the relay coil 26 and thecircuit interrupters 7 and 8 will be tripped when this current exceedsthe predetermined value for which the relay is set to operate. If oneline, for example, line 5, is out of service, then the inductive winding28 acts in effect as an auto-transformer with a 1 to 2 turn ratio,one-half of the winding being energized by a current proportional to thecurrent in the line 4 and acting as the common winding while the otherhalf of the winding acts as the series winding. Consequently the currentin the -rela coil 26 is substantially proportional to t e vectorial sumof the currents in the two lines, since the current in line 5 is, byassumption, zero. In this case, when the current in the relay coil 26exceeds the predetermined value, the circuit interrupter 7 will betripped. Thus the relay 25 is always energized by a current proportionalto the vectorial sum of the line currents, whether one or two lines arein service and therefore either line, when in service alone, may beoperated at substantially the same current as the two lines togetherwithout changing the relay adjustment.

In the previous cases of operation discussed, it has been assumed thatthe currents in the two lines are in the same direction, but therelative direction of these currents is immaterial so far as energizingthe relay 25 by a current proportional to the vectorial sum of the linecurrents is concerned. Thus assuming, that each of the lines is carryingthe same current but that these currents are flowing in oppositedirections, then the inductive winding 28 acts in effect as a balancedend reactor, that is a current proportional to the current in the line 4flows in one direction in one-half of the winding 28 and an equalcurrent proportional to the current in the line 5 flows 1n the oppositedirection in the other half of the winding 28. These currents combineand flow through the connection between the points 20 and 21 and theinductance of the winding 28 is substantially zero, so thatsubstantially no current flows in the relay coil 26. This is as itshould be, for the vectorial sum of two equal and opposite currents, asassumed, is zero.

In Fig. 2, the inductive means 24 1s illustrated as mutually inductivein the form of a transformer whose primary 29 is connected in the samemanner as the inductive winding 28 of Fig. 1, as heretobefore described,and whose secondary 30 has in circuit therewith the relay coil 26. Withthis arrangement, if we assume, for example, that the ratio of the turnsin the winding 29 to the turns in the winding 30 is 2 to 1, then therela coil 26 will be energized by a current wlnc is substantially equalto the vectorial sum of the currents in the secondaries of the currenttransformers 22 and 23. ThlS Wlll readily be understood, since one halfof the winding 29 will be energized hy a current substantially equal tothe current 1n the current transformer secondary 22 and the other halfby a current substantially equal to the current in the currenttransformer secondary 23. The resultant effect of the windin 29 istherefore substantially equal to onealf the vectorial sum of thecurrents in the current transformer secondaries 22 and 23, that isproportional to the'vectorial sum of the line currents. This resultanteffect or sum, by reason of the transformation ratio assumed, appears inthe secondary winding 30, and therefore the relay coil 26, as a currentsubstantially equal to the vectorial sum of the currents in the currenttransformer secondaries 22 and 23, that is, proportional to thevectorial sum of the line currents.

In Fig. 3, the inductive means 24 is illustrated as comprising thewinding 31 connected in the same manner as the inductive winding 28 ofFig. 1, as heretofore described. In this modification, the relay coil 26is shown as connected between the quarter points of the inductivewinding 31. This winding acts in effect as a 1 to 2 turn ratioauto-transformer, one half of the winding being energized by a currentsubstantially equa to the current in the current transformer secondary22 and the other half by a current substantially equal to the current inthe current transformer secondary 23. The resultant effect of the wholewindin is therefore substantially equal to one-ha of the vectorial sumof the currents in the current transformer secondaries 22 and 23 and byreason of the turn ratio assumed, the current appearing in the relaycoil 26 is twice as great so that the relay is energized by a currentsubstantially proportional to the vectorial sum of the line currentswhether one or both lines is or are in service.

Protective means embodying my invention is of particular value wheredifl'erential protection involvin current transformers connected inseries or'normally circulating current is provided and it is desired toprovide additional protection such that either of two parallel linesalone may carry as much current as the two together and the vectorialsum carried at any time should not exceed a predetermined value. Thisprotective means is veryA simply and economically provided, since t ereis required but one additional inductive device and a relay whoseadjustment does not have to be altered to correspond to the lines inservice.

While I have shown and described my invention and one applicationthereof in considerable detail, I do not desire to be limited to theexact arrangements and application shown, but seek to cover in theappended claims all those modifications that fall within the true spiritand scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is 1. Protective means for controlling two parallel lines wherebyeither line alone may carry as much current as the two lines together,comprising current transformers respectively connected to be energizedfrom the lines, a circuit comprising the secondaries of the currenttransformers connected in series for normally circulating current, aninductive winding connected in series in said circuit, a connection fromthe midpoint of said winding to another point of said circuit normallyat substantially the same potential, and a relay having a coil connectedacross said inductive winding, the construction and arrangement of partsbeing such that the relay is energized by a current substantiallyproportional to the vectorial sum of the line currents.

2. In a protective arrangement for an electric system wherein twoparallel lines are arranged to be controlled by circuit interrupters,means for controlling the operation of said interrupters comprising arelay and means for energizing the'relay by a current derived from theline currents and substantially proportional to the vectorial sumthereof, comprising current transformers respectively connected to beenergized from the lines, a circuit comprising the secondaries of thecurrent transformers connected in series for normally circulatingcurrent, an inductive winding connected in series in said circuit, a.connection across said circuit from an intermediate point in saidwinding, said relay havin a coil connected across said inductivewinding.

3. A protective arrangement for two parallel lines comprising currenttransformers respectively connected to be energized from the lines, acircuit comprising the secondaries of the current transformers connectedin series for normally circulating current, an inductive windingconnected in series in said circuit, a connection from an intermediatepoint of said winding to another point of said circuit normally atsubstantially the same potential, and a relay having a single energizingcoil which is connected to be energized from said inductive winding.

4. Protective means for controlling two parallel lines whereby eitherline alone may carry as much current as the two lines togethercomprising a relay and means for energizin said relay by a currentderived from the line currents and substantially proportional to thevectorial sum thereof comprising current transforniers respectivelyconnected to be energized from the lines, a circuit comprising thesecondaries of the current transformers connected in series for normallycirculating current, stationary inductive means having a windingconnected in series in said circuit, and a connection from the midpointof said winding to another point on said circuit normally atsubstantially the same potential, said rela having a coil connected incircuit with sai inductlve means.

5. A protective arrangement for two parallel lines comprising currenttransformers respectively connected to be energized from the lines, acircuit comprising the secondaries of the current transformers connectedin series for normally circulating current, stationaryinductive meanshaving a winding connected in series in said circuit, a connection froman intermediate point of said winding to another point on the other sideof said ci'rcuit normally at substantially the same po tential, and anelectroresponsive device having a single energizing coil connected to beenergized from said inductive means.

6. A protective arrangement for two parallel lines comprisingtransformers respectively connected to be energized from the lines, acircuit comprising the secondaries of the transformers connected inseries, inductive means comprising a winding connected in said circuit,a connection across said circuit from an intermediate point of saidWinding, and an electroresponsive device having a single energizing coilconnected to be energized from said inductive means.

7 In combination with two electric circuits and a circuit interrupterfor each, means for selectively controlling the opening of the circuitinterrupter in a faulty circuit and for controlling the opening of saidcircuit interrupters simultaneously including current transformersrespectively connected to be energized from said circuits, adifferential protective circuit including the secondaries of saidtransformers, a relay having a winding connected in series relation withsaid protective circuit and a relay having a winding connected in shuntrelation with said protective circuit.

8. In combination with two electric circuits and a circuit interrupterfor each, means for selectively controlling the opening of the circuitinterrupter in the circuit carrying the greater current when thedifference between the circuit currents exceeds a predetermined valueand for controlling the opening of the circuit interrupters when the sumof the circuit currents exceeds a predetermined value includingtransformers respectively connected to be energized from said circuits,a differential protective circuit including the secondaries of saidtransformers, inductive means connected in said protective circuit, arelay having a winding connected to be energized from said inductivemeans and a relay having a winding connected to be energized directlyfrom said protective circuit.

9. In combination With two parallel lines and a circuit interrupter foreach line, means for selectively controlling the opening of the circuitinterrupter in the line carrying the greater current when the differencebetween the line currents exceeds a predetermined value and forcontrolling the opening of said circuit interrupters when the sum of theline currents exceeds a predetermined value including currenttransformers respectively connected to be energized from said lines, adifferential protective circuit including the secondaries-of saidtransformers, an inductive winding connected in said circuit, aconnection across said circuit from an intermediate point of saidwinding, a relay having a winding in series relation with saidconnection, and a relay connected to be energized from said inductivewinding.

10. In combination with two parallel lines and a circuit interrupter foreach line, means for selectively controlling the opening of the circuitinterrupter in the line carrying the greater current when the differencebetween the line currents exceeds a predetermined value and forcontrolling the openin of said circuit interrupters when the sum 0 theline currents exceeds a predetermined value including currenttransformers respectively connected to be energized from said line, adifferential protective circuit including the secondaries of saidtransformers, inductive means including a winding connected in series insaid circuit, a connection across said circuit from an intermediate ointof said winding, a relay having a win ing in series relation with saidconnection and a relay connected to be energized from said inductivemeans.

In witness whereof, I have hereunto set my hand this twenty-third day ofJanuary, 1929.

OLIVER C. TRAVER.

CERTIFICATE OF CORRECTION.

Reissue Patent No. 17,601. Granted February 21. 1930, to

OLIVER C. TRAVER.

it is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 4,line 33. claim 8, after the word "including" insert the word "current";and that the said Letters Patent should be read with this correctiontherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 18th day of March, A. D. 1930.

M. J. Moore, (S al) Acting Commissioner of Patents.

